1. Field of the Invention
This invention relates in general to array antennas, and, in particular, to a lightweight modular low-level reconfigurable beamformer for array antennas.
2. Description of Related Art
Communications satellites are in widespread use. The communications satellites are used to deliver television and communications signals around the earth for public, private, and military uses.
The primary design constraints for communications satellites are antenna beam coverage and radiated Radio Frequency (RF) power. These two design constraints are typically thought of to be paramount in the satellite design because they determine which customers on the earth will be able to receive satellite communications service. Further, the satellite weight becomes a factor, because launch vehicles are limited as to how much weight can be placed into orbit.
Many satellites operate over fixed coverage regions and employ polarization techniques, e.g., horizontal and vertical polarized signals, to increase the number of signals that the satellite can transmit and receive. These polarization techniques use overlapping reflectors where the reflector surfaces are independently shaped to produce substantially congruent coverage regions for the polarized signals. This approach is limited because the coverage regions are fixed and cannot be changed on-orbit, and the cross-polarization isolation for wider coverage regions is limited to the point that many satellite signal transmission requirements cannot increase their coverage regions.
Many satellite systems would be more efficient if they contained antennas with high directivity of the antenna beam and had the ability to have the coverage region be electronically configured on-orbit to different desired beam patterns. These objectives are typically met using a phased array antenna system. However, phased array antennas carry with them the problems of large signal losses between the power amplifiers and the beam ports, because of the beamforming network interconnections and long transmission lines. Further, the beamforming network is heavy, difficult to integrate and test, and is difficult to repair or replace without large time and labor costs.
There is therefore a need in the art for a beamformer that can reduce the signal losses of a phased array antenna system. There is also a need in the art for a beamformer that is easier to integrate and test. There is also a need in the art for a beamformer that to provide more complete utilization of space assets without dramatically increasing the cost of manufacturing and operating a satellite.